Answer: Angle addition postulate.
Explanation: If and
here, if we have to prove x=30
If there is a condition that TR is a line which meets with the line segment VS at point R then by the Angle addition postulate, we can say that ⇒
But,
In option (1) substitution property of equality
If there is condition that
then we can use substitution property of equality,
And, in this case ⇒
which is wrong. So, we can not use this property here.
In option (3) subtraction property of equality
There is no use of this property to find the value x.
In option (4) addition property of equality
There is no use of this property to find the value x.